Download Synthesis, Growth and characterization of L-Histidine

International Journal of Computer Application (2250-1797)
Volume 5– No. 4, June2015
Synthesis, Growth and characterization of L-Histidine
Hydrobromide single crystal by slow evaporation method
V.Kathiravana,b, S.Parib*, P.Selvarajanc
a
Department of Physics, Government Arts College(Autonomous), Karur-5,Tamilnadu,
India. Mobile No. : 9943165869, email: [email protected]
b
Department of Physics, National College(Autonomous), Tiruchirappalli-1,
Tamilnadu, India. Mobile No. : 9443311281, email: [email protected]
c
Department of Physics, Adhitanar College of Arts & Science, Tiruchendur-16,
Tamilnadu, India. Mobile No.: 8870428536, email: [email protected]
ABSTRACT
A semi – organic nonlinear optical crystal of L-Histidine hydrobromide (LHHB) were
grown by solution method with slow evaporation technique. The solubility study was carried
out in the temperature range of (30–50) ℃ in double distilled water. The lattice parameters of
the grown crystals were determined by X-ray diffraction technique. Fourier transform
infrared (FT-IR) study reveals that the functional groups present in the crystal. The UV–VisNIR spectral studies were carried out to find the transmittance and other optical parameters.
The refractive index of the grown crystal was determined by Brewster’s angle method. The
presence of elements in the grown crystal was identified by EDAX studies. The Vicker’s
Microhardness test was carried out to test the mechanical stability and the hardness
parameters are determined. The dielectric constant and dielectric loss of the crystal was
studied as function of frequency and the results are discussed. The TG/DTA and DSC studies
confirm the thermal stability of the grown crystal. The SHG efficiency of the crystal was
found by Kurtz and Perry technique.
Key words: Single crystal; XRD; microhardness; dielectric constant; thermal studies; NLO
*
Corresponding author: [email protected]
1. INTRODUCTION
At one time natural specimens were the only source of large and well formed crystals.
Now – a- days, large crystals are being grown artificially in laboratories and being used in
many scientific and technological fields. In recent years, the need of nonlinear optical single
crystals are very much useful in the field of second harmonic generation, fiber optic
communication, electro –optic modulation, etc [1, 2]. The search for new materials with high
optical nonlinearities is an important area due to their practical applications such as optical
communication, optical computing, optical disc data storage, laser fusion reactions, remote
sensing, color display medical diagnostics,etc, [3]. Amino acids are molecules containing an
amine group, a carboxylic acid group and a side chain that varies between different amino
acids. Recent studies indicate the L-histidine favorably forms several salts with organic or
inorganic acids. The amino acids viz, L-histidine serves as a proton acceptor and as a
nucleophilic reagent. L-histidine frequently occurs at the active sites of enzymes and
co-ordinates ions on large protein structures [4]. L- histidine complexes belong to
non-centrosymmetric space groups and it is an essential criterion for Non linear optical
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applications. L-histidine hydrobromide (LHHB) is an NLO material and through scan on
literature reveals that only a limited work on various properties of this complex has been
reported [5-8]. Hence the aim of this paper to report the studies on solubility, growth, XRD
studies, FT-IR spectral studies, optical transmittance studies, refractive index measurement,
EDAX studies, thermal studies, microhardness studies, dielectric studies and SHG Studies of
grown LHHB crystal.
2. EXPERIMENTAL METHOD
2.1. Synthesis of the sample
L-histidine hydrobromide (LHHB) salt was synthesized from stoichiometric
incorporation of AR grade of L-histidine and hydrobromic acid in the molar ratio of 1:1. The
component salts were dissolved in de-ionized water and mixed thoroughly using a magnetic
stirrer at room temperature. On evaporating the solvent by heating at 50℃, the synthesized
salt was extracted. The purity of the synthesized salt was further improved by successive
recrystallization process.
2.2. Solubility
The solubility study of the synthesized LHHB salt was carried out at room temperature
30℃ by gravimetric method [9]. The synthesized salt was added step by step to 50 ml of
de-ionized water taken in a beaker kept on the hot-plate of magnetic stirrer and stirring was
continued till a small precipitate was formed. This gave confirmation of supersaturated
condition of the solution. Then, 25 ml of the solution was pipetted out in a petri dish and it
was warmed up till the solvent was evaporated out. By measuring the amount of salt present
in the petri dish, the solubility of LHHB in de-ionized water was determined. The
experiment was repeated at different temperatures. The solubility curve is shown in fig.1.
From the graph it is observed that the solubility of LHHB salt in water increases linearly
with temperature, showing a high solubility gradient and positive temperature coefficient,
which ensures the slow evaporation technique is the appropriate method to grow single
crystals of L-histidine hydrobromide.
42
40
solubility (g/100ml))
38
36
34
32
30
28
26
30
35
40
45
50
0
temperature ( C)
Fig.1. solubility curve of LHHB crystal
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2.3. Growth of crystals
Single crystal of LHHB was grown by slow evaporation technique at room
temperature. In accordance with the solubility data, the saturated solution of the synthesized
salt of LHHB was prepared and it was constantly stirred for about 6 hours using a magnetic
stirrer and was filtered using whatmann filter papers. Then the filtered solution was kept in
growth vessel covered with a porous paper and kept in a dust – free atmosphere. After a span
of 25 days, a good quality single crystal of LHHB was obtained and is shown in fig.2. The
grown crystals are found to be transparent, non –hygroscopic and colorless.
Fig.2. Photograph of the grown LHHB Crystal
2.4. Characterization methods
In order to ascertain the structure, purity and identification of the grown crystal, single
crystal X-ray diffraction data were collected using an Bruker-Nonius MACH3/ CAD4
X- ray diffractrometer with MoKα radiation (λ= 0.71069Ǻ) powder X-ray diffraction
pattern of the sample was obtained using a powder X-ray diffractometer (XPERT – PRO
Model, Nickel filtered CuKα radiations (λ=1.540Å) at 40kv, 30mA. The FT-IR spectrum of
the sample was recorded using a Perkin-Elmer FT-IR spectrometer model SHIMADZU
FT-IR 8400s by the KBr pellet technique in the range 4000-400cm-1. The optical transmission
spectrum of the crystal was carried out using a Lambda 35 model perkin Elmer double beam
UV-Vis-NIR spectrophotometer. The Thermo Gravimetric Analysis (TGA) and Differential
Thermal Analysis (DTA) were carried out for LHHB sample using a SDT Q600 V 20.9 Build
20 thermal analyzer in Nitrogen atmosphere for the temperature range 40℃-1000℃ at a
heating rate of 200C/min. Mechanical property was studied by measuring microhardness of
the grown LHHB crystal and it was carried out using Leitz Weitzler hardness tester fitted
with a diamond indenter. Second Harmonic Generation (SHG) test for the grown sample was
performed by the powder technique of Kurtz and Perry using a pulsed Nd: YAG laser
(Model: YG501C, λ= 1064nm), pulse energy of 4mJ/Pulse width of 8 ns and repetition rate
of 10 Hz were used. The measurements of dielectric constant and dielectric loss for the grown
crystals were carried out using an LCR meter (Agilent 4284A) at various frequencies in the
range 102-106 Hz at room temperature. For the good ohmic contact, opposite faces of the
sample crystal were coated with good quality silver paste.
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3. RESULTS AND DISCUSSION
3.1. Structural characterization
Single crystal X-ray diffraction analysis was carried out to determine the lattice
constants. Obtained lattice parameters of LHHB crystal are a = 7.049 Å, b = 9.055Å,
c= 15.263Å and α=900, β= 900, γ=900. The data indicates that LHHB crystal crystallizes in
orthorhombic structure [10]. To confirm the XRD data, powder XRD studies were also
carried out for the sample. The grown crystals of LHHB were crushed into fine powder and
powder X-ray diffraction analysis has been carried out using a powder X-ray diffractometer.
The recorded pattern is shown in fig.3. The sharp peaks of XRD pattern indicate high degree
of crystalline structure of grown crystal. The observed diffraction pattern has been indexed
and Miller indices were estimated by Indexing software package.
3.2. FT-IR Spectral Studies
FT-IR spectrum of the grown LHHB crystal was recorded to analyze the presence of
functional groups. The FT-IR spectrum of LHHB was presented in fig.4. The absorption
peaks from 2000- 3500 cm-1 includes overlap of absorption peaks due to O-H stretch of
–COOH and N-H stretch of NH3+. The CH2 bending mode appears at 1334.01 cm-1. The
torsional oscillation of NH3+ occurs nearly at 523.49 cm-1[11]. The complete FT-IR
assignments to the vibrational frequencies of LHHB crystal are assigned in the table (1).
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100
90
80
693.31
60
50
0
4000
3500
3000
2500
2000
1500
1000
523.49
490.42
1059.02
1334.01
1411.41
1601.51
10
2602.07
3445.30
20
1983.33
30
1137.01
961.89
909.21
863.58
40
3008.32
Transmittance (%)
70
500
-1
wave number (cm )
Fig.4. FT-IR Spectrum of LHHB crystal
Table.1. Vibrational Assignments for LHHB Crystal
Wave Number (cm-1)
Assingnments
3445.30
N-H Asymmetric stretching
3008.32
C-H stretching
2602.07
NH2+ Asymmetric and symmetric stretching
1983.33
NH3+ bending (s)
1601.51
NH3+ Asymmetric bending (vs)s
1411.41
N-H bending
1334.01
CH2 deformation
1137.01
C-H deformation (vs )
1059.02
N-H bending(s)
961.89
N-H deformation
909.21
C-H out of plane bending
863.58
C-N deformation
693.31
C=O deformation
523.49
Torsional oscillation of NH3+
490.42
O-H plane bending
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3.3. UV-Vis-NIR spectral Analysis
The UV-Vis-NIR transmittance spectrum was recorded for the grown crystal using a
UV-Vis-NIR spectrophotometer in the range 190-1100 nm, to find the suitability of LHHB
crystal for optical applications. The recorded spectrum is shown in the fig.5. The crystal
shows good transmittance in the visible region which enables it to be a good material for
optoelectronic applications. As observed in the spectrum, the LHHB crystal is transparent in
the region from 210 to 1100 nm. The lower cut- off wave length for LHHB crystal was found
at 235 nm. The wide range of transparency suggests that the crystals are good candidates for
nonlinear optical applications [12].
40
35
25
384.30
Transmittance (%)
30
20
15
10
5
0
200
400
600
800
1000
-1
wavenumber (cm )
Fig.5. UV-Visible Transmittance Spectrum of LHHB Crystal
3.4. Refractive Index Measurement
The refractive index of the LHHB crystal was determined by Brewster's angle
method. A polished single crystal of LHHB with 1mm thickness was mounted on a rotating
mount at an angle varying from 0⁰ to 90⁰. The laser was made to fall on the crystal placed in
a rotary stage. The initial angular reading, when the crystal was perfectly perpendicular to the
intra - cavity beam was noted. The transmitted light travelling through the crystal gets
polarized when the crystal has zero reflection. The angle at which the crystal has zero
reflection is called the Brewster's angle or polarizing angle (θp). Thus, the crystal was rotated
until the reflection of laser beam vanishes and the final angle was noted [13]. Brewster's
angle for LHHB was measured 56.4⁰.A He-Ne Laser of wavelength 632.8 nm was used as
the source. The refractive index was calculated as 1.505 using the formula µ=tan θp.
3.5. EDAX studies
Energy dispersive X-ray spectroscopy (EDAX) was used to identify the elements
present in the grown LHHB crystal. The EDAX spectrum was recorded using Jeol 6390 LV
model scanning electron microscope and it is shown in the fig.6. From the results, it is
confirmed that the elements such as carbon, oxygen, bromine and Nitrogen are presented in
the sample. It is to be mentioned here that hydrogen cannot be identified from the sample by
EDAX method. The weight percentage of hydrogen in the sample, from CHN analysis was
carried out. The weight percentage of the different elements in the grown crystal of LHHB is
given in the table.2.
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Fig.6. EDAX Spectrum of LHHB Crystal
Table.2.The elemental composition of the grown LHHB crystal
Element
Carbon
Oxygen
Nitrogen
Bromine
Hydrogen
Weight percentage (%)
23.110%
15.34%
16.539%
31.449%
4.760%
3.6. Microhardness Measurement
Hardness is one of the important mechanical properties of solid material. It can be used
as a suitable measure of the plastic properties and strength of the material. Microhardness
testing is one of the best methods of understanding the mechanical properties of materials
such as fracture behavior, yield strength, brittleness index and temperature of cracking.
Transparent crystals free from cracks were selected for microhardness measurements. Before
indentations, the crystals were carefully lapped and washed to avoid surface effects.
Microhardness analysis was carried out using Vicker’s microhardness tester fitted with a
diamond indenter. The well polished LHHB crystal was placed on the platform of the Vickers
microhardness tester and the loads of different magnitude were applied over a fixed interval
of time. The indentation time was kept as 10 sec for all the loads. The hardness was
calculated using the relation Hv = 1.8544 P/d2 in kg/mm2, where P is the applied load in Kg
and d is the diagonal length of the indentation impression in millimeter [14]. The relation
between hardness number (Hv) and load (P) for LHHB crystal is shown in fig.7. The hardness
increases gradually with the increase of load. The relation between load and size of the
indentation is given by well known Meyer’s law P=adn.
Here ‘a’ and ‘n’ are constants
depending upon the material. The value of the work hardening coefficient n was found to be
2.1203 from the fig.8. According to Onitsch, 1.0 ≤ n ≥ 1.6 for hard materials and n >1.6 for
soft materials [15]. Hence, it is concluded that LHHB belongs to the soft category materials.
Other mechanical properties such as yield strength (σy) and stiffness constant (C11)
were calculated at different loads. The relations for determining yield strength
(σy= (Hv/3) N/m2) and the stiffness constant (C11= (Hv)7/4 N/m2) where Hv is the Vicker’s
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microhardness number of the material [16]. The variations of yield strength and stiffness
constant for LHHB crystal with the applied loads are shown in the figs. (9) and (10). It is
observed from the results that the mechanical properties like hardness, yield strength and
stiffness constant increase with increase in the applied load.
96
94
2
Hv (Kg/mm )
92
90
88
86
84
82
80
0
50
100
150
200
Load P (g)
Fig.7. plot of Load versus Hv for LHHB crystal
2.4
Equation
y=a+b
Adj. R-Squ 0.99986
Value
2.2
Standard Er
B
Intercept -1.502
0.01922
B
Slope
0.01268
2.1203
2.0
Log P
1.8
1.6
1.4
1.2
1.0
0.8
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
Log d
Fig.8. plot of Log d versus Log P for LHHB crystal
310
2
V ( X 10 N/m )
300
6
290
280
270
260
0
50
100
150
200
Load P (g)
Fig.9. plot of Load versus yield strength for LHHB crystal
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42
40
2
C11 ( X 10 N/m )
38
14
36
34
32
30
0
50
100
150
200
Load P (g)
Fig.10. plot of Load versus stiffness constant for LHHB crystal
3.7. Dielectric Studies
The dielectric studies were carried out for LHHB crystal. Fig.11. shows the variation
of dielectric constant with frequency for the LHHB crystal. The dielectric constant εr
decreases with applied frequency. The very high value of εr at low frequencies may be due to
the presence of all the four polarizations namely, space charge, orientation, electronic and
ionic polarization and its low value at higher frequencies may be due to the loss of
significance of these polarizations gradually[17,18].
The variation of dielectric loss with frequency is shown in fig.12. As these materials
shows low dielectric loss with high frequency this sample possesses enhanced optical quality
with lesser defects. This is an important parameter of vital importance for Non Linear Optical
applications [19,20].
40.6
40.4
dielectric constant (r)
40.2
40.0
39.8
39.6
39.4
39.2
39.0
2.6
2.8
3.0
3.2
3.4
3.6
log f
Fig.11. variation of dielectric constant with log frequency
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0.030
0.025
dielectric loss
0.020
0.015
0.010
0.005
0.000
2.6
2.8
3.0
3.2
3.4
3.6
log f
Fig.12. variation of dielectric loss with log frequency
3.8. Thermal studies
The TG/DTA and DSC thermal traces for LHHB crystal are shown in the fig.13. The
fig.13.shows that the sample is thermally stable upto 143℃ and the weight loss starts above
this temperature. The weight percentage of about 21% observed at 150℃ may be attributed to
the loss of lattice water [21]. From differential thermal analysis curve, it is observed that
sample shows an endothermic peak at 267℃ which corresponds to the decomposition point of
the sample. This endotherm closely matches with the major weight loss in TGA analysis.
From the DSC curve in the fig.13, it is also confirmed that the LHHB crystal has water of
crystallization and the decomposition point of the sample is at 143℃.
Fig.13. Thermal Analysis of LHHB Crystal
3.9. Non Linear optical studies (NLO)
The NLO behavior of the LHHB crystal was evaluated by the Kurtz and Perry method
[22]. The emission of green light from the powdered sample, using Nd:YAG laser beam of
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λ=1064nm, confirmed the second harmonic generation (λ=532nm). The powder SHG
efficiency was found to be 0.92 times that of KDP [23].
4. CONCLUSION
L-histidine hydrobromide (LHHB) crystals were grown successfully by slow
evaporation method. LHHB crystal has positive temperature co-efficient to solubility, XRD
studies reveal that LHHB crystal crystallizes in orthorhombic structure. FT-IR analysis
confirmed the presence of various functional groups in the grown LHHB crystal. The
UV-Vis-NIR spectral studies confirmed that the grown crystal has wide transparency in the
visible region, the good transparency shows that LHHB crystal can be used for non-linear
optical applications. The refractive index value was determined to be 1.505, this value shows
that the grown crystal is suitable for optical applications. Various elements present in the
sample have been identified by EDAX studies. The Vicker’s microhardness study of the
crystal was carried out and the crystal is found to be soft material category and suitable for
device fabrication. The dielectric constant and dielectric loss of the crystal decreases with
increase in frequency and these low values at high frequencies reveals the desirable property
of the crystal for NLO device applications. The thermal stability is confirmed by the thermal
analysis. NLO studies reveals that the suitability of the grown crystal for NLO applications.
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